What is the return/throw state of Publisher.values if there is no error and no values

I'm converting some Combine publishers to async using .values and trying to understand what happens when:

A Publisher completes before emitting a value.

Here is some example code:

let response = client.fetch(query: query)
  .tryMap { 
   /* map the data, or throw a mapping error if it doesn't map. */
    }
    return Model()
  }
  .eraseToAnyPublisher()
  .values
for try await result in response {
  return result
}
throw AsyncCombineError.finishedWithoutValue // my custom error

What happens with .values if the publisher completes without emitting any values? It returns a type of AsyncThrowingSequence<Self>

Will it throw? return? hang? or is this state impossible to happen?

Thanks and please enlighten me if I am misunderstanding structured concurrency. This is new to me!